In order to have a meeting involving participants not located in the same area, a number of technological systems are available. These systems may include video conferencing, web conferencing and audio conferencing.
The most realistic substitute for real meetings is high-end video conferencing systems. Conventional video conferencing systems comprise a number of endpoints communicating real-time video, audio and/or data streams over WAN, LAN and/or circuit switched networks. The endpoints include one or more monitors, cameras, microphones and/or data capture devices and a codec, which encodes and decodes outgoing and incoming streams, respectively. In addition, a centralized source, known as a Multipoint Control Unit (MCU), is needed to link the multiple end-points together. The MCU performs this linking by receiving the multimedia signals (audio, video and/or data) from endpoint terminals over point-to-point connections, processing the received signals, and retransmitting the processed signals to selected endpoint terminals in the conference.
Video conference systems are used throughout the business community for point to point audio and visual communication between individuals. The users of video conferencing may sit in workplace environments such as personal office or cubical, small or large meeting rooms or board rooms. They may also sit in other types of environments such as school classroom, auditoriums, prison visitation rooms, or public areas such as airports, train stations, libraries, hotel lobby, manufacturing plants etc. Portable self contained systems have been developed enabling users to communicate from e.g. desert expeditions, mountain climbing, oil platforms, etc. In essence a video conferencing system may be in use in any inside or outside environment anywhere in the world.
Hence, video conferencing systems operate in many cases under widely varying lighting conditions, ranging from office environments with fluorescent ceiling lights and halogen lamps to a partly or fully outdoor environment with strong exposure to natural sunlight. The performance of most if not all face recognition systems is strongly affected by many environmental lighting conditions.
The light intensity can vary from weak and diffuse to high intensity spot. In most of the usage scenarios the user is not able to adjust the lighting; rooms will have permanently fitted ceiling lights, windows allowing daylight, etc. Small adjustments may be possible through the use of curtains or blinds, turning on or off ceiling lights etc, but in most situations the user has to accept the conditions as they are.
Also, changing the position and orientation of the capture device (that is, a camera) usually affects the recorded illumination of the subject. Furthermore, environments affected by sunlight will have different lighting conditions at different times of the day.
The enormous variation is ambient lighting results in the video conference user being illuminated in a variety of ways, only some of which are suitable for a high quality video conference. Extreme situations may result in the user being backlit with strong sunshine which even although damped by blinds or curtains may still give a silhouette appearance to the other video conference users. This will result in the other users of the video conference communicating with a silhouette instead of a visible person.
A common bad lighting situation in a video conference appears when the participants are using personal desktop video conferencing endpoints in office environments. In these cases, the camera is typically localized relatively closed to the user's face, normally on top of the desktop endpoint. In office environments, strong fluorescent lighting from above typically creates shadows in the user's face making a distorted and blurred face image.
A general advantages of video conferencing compared to audio conferencing is that it allows for exchange of expressions just as in real face-to-face communication. This advantage could be completely spoiled when the face lighting is bad.
This is particularly important in cases of use in the judicial system is it vital that the judge, prison guard or arresting officer can evaluate the prisoners' sobriety and general condition by looking at his facial features, reactions and expressions. The prisoners' facial features, contours, shadows under the eyes will all vary dramatically depending on the direction of the ambient lighting, given that it may come from ahead, behind, above or from the side.
Use of systems in outside applications, such as expeditions or emergency response services may easily result in the situation whereby a system is required to operate in low-light or no-light situation. In such conditions a portable video conferencing systems designed for outside rugged use will not be able to function.
One attempt to solve the above described problems is the Sightlight, developed by Griffin Technology for the Apple iSight (ref.: www.griffintechnology.com/products/sightlight/), which is a product providing a source of illumination to webcam users. The Sightlight is designed as a ring of LEDs mounted within an optical reflector formed as a circular ring that fits around the cylindrical body of the Apple iSight. The Sightlight has three switching modes, being on, off or auto adjust. The auto adjust is accomplished by use of a photo diode sensing the level of ambient brightness. The Sightlight is relatively weak in light power, only being able to illuminate a face when approximately 40 cm from the unit. Further away than 40 cm gives no change to the perceived illumination when viewed through the video conference system.
Another drawback of the Sightlight is the location of the light source, i.e. the location in a circular pattern around the camera. This results in the user looking at the screen with the light source mounted directly above the screen (for nearest possible eye-to-eye contact) and being distracted by the spotlight effect of the Sightlight. The optical lens only splits the light source from the LEDs into smaller refracted light beams, with no attempt being made to diffuse the light. The effect can be described as to being similar to looking into the beam of a torch.
The Sightlight is only controllable from the near-end of the web-cam system, i.e. it is controlled by the user that is being illuminated. It is not possible to remotely control the Sightlight from the far-end, i.e. from the users looking at the user being illuminated.